Questions

When atoms react they do so in order to reach the lowest energy, which is the most stable. The electrons orbitals will overlap in the way that reduces the energy the most. Orbitals of similar energy will produce the greatest stabilisation.The answer you gave isn't the whole story, it depends what species is reacting with what. The effective nuclear charge on the atom will affect the energy of the valance electrons.

Hence, the reactivity of an atom arises from the existence of unpaired electrons in the valence shell.

Here the given Number Puzzle follows a pattern that, Sum of the numbers on the corners on the two squares is same and is equal to 54.

i.e,

13 + 15 + 14 + 12 = 54 

and

8 + 22 + 9 + 15 = 54

Khan Abdul Ghaffar Khan

Second ozone hole was detected over Tibet in the year 2006. 

Ozone is a form of oxygen, acts as a high-altitude atmospheric screen against cancer-causing ultraviolet light.

The main source of these halogens in the stratosphere is photodissociation of man made halocarbon refrigerants, solvents, propellants and CFC's.

Here it is an idiom that says The cricket match proved to be a big draw means it stands as a huge attraction.

The Rolling plan refers to one-year plans in the five-year perspective. under Rolling plan, there would be an annual appraisal of the progress of the plan and on the basis of such an appraisal, the plan for the next year will be prepared. The plan would go on rolling year after year.